Natural kinds and dispositions: A causal analysis

Objects have dispositions. Dispositions are normally analyzed by providing a meaning to disposition ascriptions like ‘This piece of salt is soluble’. Philosophers like Carnap, Goodman, Quine, Lewis and many others have proposed analyses of such disposition ascriptions. In this paper we will argue with Quine (‘Natural Kinds’, 1970) that the proper analysis of ascriptions of the form ‘x is disposed to m (when C)’, where ‘x’ denotes an object, ‘m’ a manifestation, and ‘C’ a condition, goes like this: (i) ‘x is of natural kind k’, and (ii) the generic ‘ks are m (when C)’ is true. For the analysis of the generic, we propose an analysis in terms of causal powers: ‘ks (when C) have the causal power to m’. The latter, in turn, is analyzed in a very precise way, making use of Pearl’s probabilistic graphical causal models. We will show how this natural kind-analysis improves on standard conditional analyses of dispositions by avoiding the standard counterexamples, and that it gives rise to precise observable criteria under which the disposition ascription is true.